System for automatic inspection of periodic patterns
US4969198A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 16, 1988 |
| Grant date | Nov 6, 1990 |
| Priority date | — |
| Expiry date | May 16, 2008 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06T2207/30148
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A method and apparatus for automatic inspection of periodic patterns typically found on patterned silicon wafers, printed circuit board, and the like is disclosed herein. The method comprises an inspection algorithm of two parts: a low-level algorithm and a higher level algorithm. The low-level algorithm utilizes the known periodically of the pattern to find defects by comparing identical cells in the periodic array. The high-level algorithm applies the low-level algorithm, some number of times (N) in succession on the image; accumulates defective pixels to form a separate image; and then applies a threshold-sort operation on a neighborhood to determine center pixel defectiveness. The apparatus for implementing the above method comprises a parallel/pipeline architecture for high speed processing and RAM LUT's to implement a plurality of subtract and compare functions.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.